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/* Pseudo random number generation functions derived from the drand48()
* function obtained from pysam source code.
*
* This functions are used in order to replace the default math.random()
* Lua implementation with something having exactly the same behavior
* across different systems (by default Lua uses libc's rand() that is not
* required to implement a specific PRNG generating the same sequence
* in different systems if seeded with the same integer).
*
* The original code appears to be under the public domain.
* I modified it removing the non needed functions and all the
* 1960-style C coding stuff...
*
* ----------------------------------------------------------------------------
*
* Copyright (c) 2011, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <stdint.h>
#define N 16
#define MASK ((1 << (N - 1)) + (1 << (N - 1)) - 1)
#define LOW(x) ((unsigned)(x) & MASK)
#define HIGH(x) LOW((x) >> N)
#define MUL(x, y, z) { int32_t l = (long)(x) * (long)(y); \
(z)[0] = LOW(l); (z)[1] = HIGH(l); }
#define CARRY(x, y) ((int32_t)(x) + (long)(y) > MASK)
#define ADDEQU(x, y, z) (z = CARRY(x, (y)), x = LOW(x + (y)))
#define X0 0x330E
#define X1 0xABCD
#define X2 0x1234
#define A0 0xE66D
#define A1 0xDEEC
#define A2 0x5
#define C 0xB
#define SET3(x, x0, x1, x2) ((x)[0] = (x0), (x)[1] = (x1), (x)[2] = (x2))
#define SETLOW(x, y, n) SET3(x, LOW((y)[n]), LOW((y)[(n)+1]), LOW((y)[(n)+2]))
#define SEED(x0, x1, x2) (SET3(x, x0, x1, x2), SET3(a, A0, A1, A2), c = C)
#define REST(v) for (i = 0; i < 3; i++) { xsubi[i] = x[i]; x[i] = temp[i]; } \
return (v);
#define HI_BIT (1L << (2 * N - 1))
static uint32_t x[3] = { X0, X1, X2 }, a[3] = { A0, A1, A2 }, c = C;
static void next();
int32_t redisLrand48() {
next();
return (((int32_t)x[2] << (N - 1)) + (x[1] >> 1));
}
void redisSrand48(int32_t seedval) {
SEED(X0, LOW(seedval), HIGH(seedval));
}
static void next() {
uint32_t p[2], q[2], r[2], carry0, carry1;
MUL(a[0], x[0], p);
ADDEQU(p[0], c, carry0);
ADDEQU(p[1], carry0, carry1);
MUL(a[0], x[1], q);
ADDEQU(p[1], q[0], carry0);
MUL(a[1], x[0], r);
x[2] = LOW(carry0 + carry1 + CARRY(p[1], r[0]) + q[1] + r[1] +
a[0] * x[2] + a[1] * x[1] + a[2] * x[0]);
x[1] = LOW(p[1] + r[0]);
x[0] = LOW(p[0]);
}
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